The present invention relates to a flash ROM management method and apparatus in, e.g., a computer. The present invention also relates to an IC card and an electronic camera using a flash ROM.
Various types of flash ROMs are currently available and roughly classified into those developed for flash disks and those developed for BIOSs of personal computers.
The erase unit of the former flash ROM is 512 bytes which is a general erase unit of hard disks. Therefore, this flash ROM is highly compatible with file systems. The erase unit of the latter flash ROM is a large block unit, e.g., 64 KB. Also, some of flash ROMs of this type require a voltage of 12 V or higher as a write voltage as in the case of PROMS. Although flash ROMs of the latter type are readily obtainable because they are inexpensive, they are not highly compatible with file systems and hence cannot be used as particularly small-capacity recording media.
As described above, flash ROMs designed for BIOSs are inexpensive and therefore readily available although they have a large erase unit and are not highly compatible with file systems. Accordingly, if this type of flash ROMs can be applied to file systems, inexpensive small-capacity recording media can be provided.
IC cards inserted into host apparatuses are widely used as auxiliary storages for storing various data. For example, an IC card which only reads out data, such as an IC card storing font data, incorporates a ROM storing necessary data. An IC card in which data is rewritable generally incorporates a RAM, and a data read/write operation is executed by using the RAM. Since, however, a RAM cannot hold data without being backed up by a power supply, a power supply is incorporated in an IC card if it is necessary to hold data.
A flash ROM is an example of the data rewritable ROM. Various types of flash ROMs are presently available and roughly divided into a category developed for flash disks and a category developed for BIOSs of personal computers.
Generally, IC cards require a dedicated interface, and so it is not possible to use interfaces for common file systems (e.g., hard disks and floppy disks) which host apparatuses have.
In electronic cameras, image data obtained by photography is stored in a storage medium such as an internal DRAM or an external memory card. These storage media need to be constantly backed up by, e.g., batteries since the stored contents disappear if the supply of power is cut off. A magnetic disk is an example of a storage medium which does not require electrical backup to hold the stored contents. However, magnetic disk devices are relatively large and therefore impair the portability of electronic cameras. Another example of a storage medium which need not be electrically backed up to hold the stored contents is a rewritable ROM, i.e., a flash ROM.
As described above, flash ROMs designed for BIOS have a large erase unit and a low compatibility with file systems but are readily obtainable because they are inexpensive. Therefore, if this type of flash ROMs can be applied to system files, it is possible to provide inexpensive, small-capacity, and small-sized recording media which do not require a power supply to hold the stored contents. This is convenient as a storage medium of an electronic camera.